Burner



E. C. MILLER Aug. 31, 1965 BURNER 2 Sheets-Sheet 1 Original Filed Aug. 16, 1962 INVENTOR EARLE 0. MILLER v w/MXQ I);

ATTORNEY E. C- MILLER Aug. 31, 1965 BURNER 2 Sheets-Sheet 2 Original Filed Aug. 16, 1962 1/ l1 1/ 1/ r// (I EARLE G. MILLER INVENTOR s Ciaims. or. res-1.5

This invention relates to a burner and, more particularly, to apparatus arranged to burn fuel in the combustion chamber of a steam generating unit. This is a continuation of patent application Serial Number 217,322, filed August 16, 1962, now abandoned.

In some areas of the world the gases leaving the stack of a steam generating unit have been suspected of contributing to air pollution. In particular, the presence of nitrous oxide in the flue gas has been suggested as the culprit. Furthermore, the presence of nitrous oxide is suggestive of the fact that complete combustion is not taking place in the furnace since, if proper combustion were taking place, nitric oxide would be formed instead of nitrous oxide. Experimental work has shown that the percentage of nitrous oxide in the flue gas increases with air velocity in the burner and is at a maximum allowable value when theair velocity in the burner is around 7,000 feet per minute. On the other hand, a burner must be designed so that it operates effectively at any load at which the steam generating unit may be operated. If the size of the burner is selected so that the air velocity is low at high loads, then it is so low at low loads that the burner cannot operate. These and other difficulties experienced with the prior art have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the present invention to provide a burner in which the air velocity passing therethrough is not excessive at high loads and is not unduly low at low loads.

Another object of the present invention is the provision of a burner which operates to produce a low quantity of nitrous oxide in the flue gases of a steam generating unit.

Another object of the invention is the provision of a burner having novel means for introducing air into the products of combustion after they leave the main portion of the burner.

Another object of the instant invention is the provision of a burner having a means of regulating the velocity of air in a burner and of regulating the manner in which it mixes with the fuel.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms as illustrated by the accompanying drawings in which:

FIG. 1 is a vertical sectional view of a burner embodying the principles of the present invention;

FIG. 2 is a generally elevational view of the burner taken on the line IIII of FIG. 1;

FIG. 3 is a sectional view of the burner taken on the line III-III of FIG. 1;

FIG. 4 is an enlarged view of a fuel gun used in the burner with portions broken away; and

FIG. 5 is an enlarged sectional view of the tip of the burner.

Referring first to FIGS. 1, 2, and 3, which show the general features of the invention, the burner, indicated generally by the reference numeral 10, is shown as mounted on a furnace 11 having water-wall tubes 12 United States Patent 0 3,203,463 Patented Aug. 31, 1965 which are bent to provide three vertically-elongated main openings 13, 14, and 15. In the preferred embodiment, the burner is mounted on the under-surface of an abutment in a furnace of the type shown and described in the patent of Miller No. 2,947,289. Mounted on the outside of the furnace wall rearwardly of the water-wall tubes 12 is a burner housing 16 defining an air plenum chamber 17. Extending rearwardly of the tube openings within the plenum chamber is a metal shroud 18 which is divided by metal walls 19 and 21 into a large principal passage or main opening 22 and smaller upper and lower auxiliary passages or openings 23 and 24. Mounted centrally of the main opening 22 is a fuel gun 25 whose front end rests in a perforated plate 26 which is mounted in the opening 13. Above and below the fuel gun 25 are adjustable vanes 27 mounted in a similar manner to those shown in the patent of Craig No. 2,759,460. Angularly adjustable vanes 28 and 29 are also provided in the auxiliary openings 23 and 24, respectively. At the rear of the shroud 18 in the auxiliary openings 23 and 24 are mounted pivoted dampers 31 and 32, respectively, which are joined by a linkage 33 to a linear actuator such as a hydraulic cylinder 34. The upper dampers 27 and 28 operate together and are adjustable by a hand wheel 35 located outside of the housing 16 and connected to the vanes by a linkage 36. The lower vanes 27 and 29 also operate together and are adjusted by means of a linkage 3'7 operated by a hand wheel 38. An ignition gun 39 of the type shown in the patent of'Thomasian et al. No. 3,007,084 extends into the main opening 22 below the fuel gun 25. Other fuel guns 41 and 42 are mounted in the openings 14 and 15, respectively, and rest on perforated plates mounted across the openings.

An air duct 43 from a source of air, such as a forced draft fan and air heater (not shown), enters the bottom part of the burner housing 16 and is provided with an adjustable damper 40 which controls the flow of air into the burner in accordance with the load on the unit. A conduit 44 is mounted in the furnace wall and extends into the furnace chamber just under the burner. A similar conduit 45 is mounted in the burner housing and extends into the duct 43 upstream of the damper 40. These two conduits are connected to a main control 46 and furnishes them with a signal which represents the drop in pressure through the burner and, therefore, represents the velocity of air flow through the burner. The output side of the main control 46 is connected by conduits 47 and 48 to the hydraulic cylinder 34. The main control is of a well-known type which receives an input signal through the conduits 44 and 45; in response to that signal, the main control provides the lines 47 and 48 and the hydraulic cylinder 34 with pressure oil flowing in either direction to actuate the cylinder.

FIGS. 4 and 5 show details of the fuel gun 25. The gun provides for a mixture of primary air and a fuel which may be oil, pulverized coal, or gas; the burner shown in the preferred embodiment is intended for use with gas. The gun is provided with a nose 49 having a frusto-conical surface 51 in which are provided apertures 52. At the outer end of the surface 51 it merges with a cup-shaped concave surface 53 which is provided with apertures 54.

The operation of the invention will now be readily understood in view of the above description. Air enters the burner through the duct 43, the amount being regulated by the damper 40. The air will be selected by a main fuel-and-air feed control (not shown) to be commensurate with the amount of fuel introduced through the fuel guns. This air will be low in quantity at low load operation of the steam generating unit and high in quantity at high load operation. In the case of a conventional burner this would mean a high air-fuel velocity at high load and low fuel-air velocity at low load. However, at no time could this velocity be allowed to drop below a minimum value necessary to maintain ignition in the burner so that the velocity at high load is very high.

The initial ignition of the fuel and air is brought about by the ignition gun 39 which continues to operate to assure that ignition is not lost by an accident in the furnace. The conduits 44 and 45 send a signal to the main control 46 indicative of the pressure loss and, therefore, of the air flow through the burner. At low load the main control will maintain this flow at a predetermined value and, for that purpose, will maintain the dampers 31 and 32 in closed condition so that very little air flows through the auxiliary openings 23 and 24. As the steam generating unit is converted to high load operation, the air flowing into the burner through the duct 43 and over the damper will increase; the pressure drop through the burner will be indicated in the conduits 44 and 45 and this fact will be transmitted to the main control 46. A signal will be sent out along the conduits 47 and 48 to the hydraulic cylinder 34 and its piston will move, operating through the linkage 33 to change the angular aspect of the dampers 31 and 32 relative to the flow or air. As a matter of fact, at high load these dampers will be parallel to the flow and the air will be free to flow into the auxiliary openings 23 and 24. Since the air introduced through the auxiliary openings 23 and 24 is spaced a considerable distance from the guns 25, 41, and 42, it will not take an active part in the initial combustion of the fuel, but will enter the fuelair mixture and the products of combustion at a point further along in the combustion chamber. They will in a general way, therefore, act to burn any incombustibles which were not consumed in the initial combustion in the burner. The main control 46 is adjusted so that it will operate to maintain the air velocity through the burner below the pre-determined value of 7,000 feet per minute. The net effect will be that the amount of nitrous oxide in the flue gases will be kept below a desired value. Naturally, of course, the velocity in the burner may be regulated to any value (commensurate with the fuel being used) to maintain the nitrous oxide below a pre-determined maximum value. In every case, of course, this velocity will be greater than the minimum value at which proper combustion and ignition may be maintained.

It is obvious that minor changes may be made in the form and construction of the invention without departing -from the material spirit thereof. It is not, however, de-

sired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to be secured by Letters Patent is:

1. In combination with a furnace wall including Waterwall tubes having a main opening extending therethrough by bending said water-wall tubes,

(:1) a burner comprising a shroud extending at a right angle to the plane of the furnace wall and surrounding the said main opening,

(b) an air plenum chamber behind the opening,

(c) a wall extending across the shroud and dividing the shroud into a principal passage and an auxiliary passage,

(d) a fuel gun located centrally of the principal passage,

(e) adjustable vanes mounted in the principal passage,

the auxiliary passage permitting flow of air at a position spaced from the gun,

(f) a regulator controlling the flow of air through the auxiliary passage, and

(g) control means measuring the velocity of air through the main opening and adjusting the said auxiliary passage regulator to maintain the said velocity below a pre-determined value irrespective of load.

2. In combination with a furnace wall including waterwall tubes having a main opening extending therethrough by bending said water-wall tubes,

(a) a burner comprising a shroud extending at a right angle to the plane of the furnace wall and surrounding the said main opening,

(b) a wall extending across the shroud and dividing the shroud into a principal passage and a pair of auxiliary passages, the auxiliary passages being located above and below the principal passage whereby air may pass into the furnace at positions spaced substantially from the principal passage,

(0) a fuel gun located centrally of the principal passage,

(d) an adjustable damper controlling flow of air through each auxiliary passage, and

(e) control means measuring the velocity of air through the main opening and adjusting the said auxiliary passage dampers to maintain the said velocity below a predetermined value irrespective of load.

3. In combination with a furnace wall including waterwall tubes having a main opening extending therethrough by bending said water-wall tubes,

(a) a burner comprising a shroud extending at a right angle to the plane of the furnace wall and surrounding the said main opening,

(b) a wall extending across the shroud and dividing the shroud into a principal passage and an auxiliary passage, the auxiliary passage permitting air to pass into the furnace at a position substantially spaced from the principal passage,

(c) a regulator controlling the flow of air through the auxiliary passage, and

(d) air velocity control means measuring the drop in air pressure through the main opening and adjusting the said auxiliary passage regulator to maintain the said pressure below a pre-determined value despite changes in load.

4. In combination with a furnace wall including waterwall tubes having a main opening extending therethrough by bending said water-wall tubes,

(a) a burner comprising a shroud extending at a right angle to the plane of the furnace wall and surrounding the said main opening,

(b) an air plenum chamber behind the opening,

(c) a wall extending across the shroud and dividing the shroud into a principal passage and a pair of auxiliary passages,

(d) a fuel gun located centrally of the principal passage,

(e) adjustable vanes mounted in the opening, the pair of auxiliary passages being located at substantially spaced positions above and below the principal passage through which air may also pass into the furnace.

(f) an adjustable damper controlling the flow of air through each auxiliary passage, and

(g) air velocity control means measuring the drop in air pressure through the main opening and adjusting the said auxiliary passage damper to maintain the said passage below a pre-determined value despite changes in load.

5. In combination with a furnace wall including water- Wall tubes having a main opening extending therethrough by bending said water-wall tubes,

(a) a burner comprising a shroud extending at a right angle to the plane of the furnace wall and surrounding the said main opening,

(b) adjustable vanes mounted in the main opening to control the character of the flame,

(c) a wall extending across the shroud and dividing the shroud into a principal passage and an auxiliary pas- Sage, the auxiliary passage being located at a position substantially spaced from the principal passage and References Cited by the Examiner being formed so that air may also pass into the. fur- UNITED STATES PATENTS nace through it, (d) an adjustable vane in the auxiliary pasage for con- 5 9/35 Lqndgren 122 235 ,229,068 1/41 Frlsch l10104 trolling the d1rect1on of the arr passing therethrough, 5 2 947 289 8/60 Miner 122479 (e) a regulator controlling the flow of air through the auxiliary passage, and FOREIGN PATENTS (f) control means measuring the velocity of air through 1,111,317 10/55 France.

the main opening and adjusting the said auxiliary 720,666 12/54 Great Britain.

passage regulator to maintain the said velocity below 10 a pre-determined value irrespective of load. JAMES WESTHAVER Primary Examine"- 

1. IN COMBINATION WITH A FURNACE WALL INCLUDING WATER WALL TUBES HAVING A MAIN OPENING EXTENDING THERETHROUGH BY BENDING SAID WATER-WALL TUBES, (A) A BURNER COMPRISING A SHROUD EXTENDING AT A RIGHT ANGLE TO THE PLANE OF THE FURNACE WALL AND SURROUNDING THE SAID MAIN OPENING, (B) AN AIR PLENUM CHAMBER BEHIND THE OPENING, (C) A WALL EXTENDING ACROSS THE SHROUD AND DIVIDING THE SHROUD INTO A PRINCIPAL PASSAGE AND AN AUXILIARY PASSAGE, (D) A FUEL GUN LOCATED CENTRALLY OT THE PRINCIPAL PASSAGE, (E) ADJUSTABLE VANES MOUNTED IN THE PRINCIPAL PASSAGE, THE AUXILIARY PASSAGE PERMITTING FLOW OF AIR AT A POSITION SPACED FROM THE GUN, (F) A REGULATOR CONTROLLING THE FLOW OF AIR THROUGH THE AUXILIARY PASSAGE, AND (G) CONTROL MEANS MEASURING THE VELOCITY OF AIR THROUGH THE MAIN OPENING AND ADJUSTING THE SAID AUXILIARY PASSAGE REGULATOR TO MAINTAIN THE SAID VELOCITY BELOW A PRE-DETERMINED VALUE IRRESPECTIVE OF LOAD. 